The present invention relates to concrete molding machines, and more particularly to a press for a concrete molding machine employing a reciprocating tamper.
Concrete molding machines are well known in the art, and generally include a feed drawer to receive a concrete mix from a feed hopper and deliver the mix to a preformed mold. The raw or unhardened concrete contained in the feed drawer is generally deposited by gravity into the mold while the mold is being vibrated.
In concrete molding machines such as those utilized for molding concrete blocks, it is desirable to eject or remove the molded concrete block from the mold as soon as possible, and to provide a block having uniform density and strength. In order to accomplish this, it is generally necessary to press or compact the raw concrete mix in the mold while the mold is vibrated.
Various arrangements are known for pressing or compacting the concrete while in the mold. One such arrangement is shown in Moore, U.S. Pat. No. 3,781,156 which discloses a concrete molding machine having a reciprocating tamper operated in response to air pressure applied to the piston of a pneumatic cylinder. Another arrangement is shown in Kitahara, U.S. Pat. No. 4,111,627 which discloses a concrete molding machine having a plunger mounted on a supporting frame. The plunger is pressed against the concrete in a mold by means of oil pressure applied to the pistons of a pair of hydraulic cylinders, and by the resilience of a pair of springs encircling the outer ends of the pistons. Another arrangement is shown in Rybicki, U.S. Pat. No. 3,225,411 which discloses an apparatus for compressing finely divided clay material into a brick. The Rybicki apparatus includes a pair of pneumatically operated spike hammers which repeatedly strike a pair of die plates to compress the clay material. Further, Kitahara, U.S. Pat. No. 4,265,609 discloses a concrete molding machine having a press plate which applies pressure against the concrete in a mold. The press plate is actuated by means of a piston rod of a hydraulic cylinder.